Mystery holes in popular Lake Michigan sand dune cause summer closure

A popular spot in the Indiana Dunes National Lakeshore will remain closed for the summer because of the mysterious appearance of holes in the 126-foot sand dune's surface.

Last July, a six-year-old boy was almost killed when a collapsing hole at Mount Baldy buried him in sand. Since then, two more holes and some depressions have been found.

So far scientists cannot explain why. That's despite the use of ground-penetrating radar and research analysis by scientists from the National Park Service, Indiana University, and the Indiana Geological Survey.

Scientists are getting ready for a more comprehensive investigation of the sand dune this summer.

The holes don't last long. They remain open for less than 24 hours before collapsing and filling in with surrounding sand, according to a statement from the National Park Service.

Garry Traynham, acting superintendent of the Indiana Dunes National Lakeshore, said the closure of Mount Baldy is a matter of public safety.

"In order to protect the public, until we can determine what is causing those holes and develop a strategy to mitigate those holes, it's imperative that we secure the site and not allow the public to have access immediately to that area," he said.

Traynham said it is not possible to predict when Mount Baldy will reopen until the results of the investigation are known.

While the dune is closed, officials will continue to plant marram grass on the parts of the dune where the native grass used to grow. This may help prevent erosion and more holes from opening up.

All other beach access areas in the park are currently open. Visitors are being asked to stay on established trails to stave off erosion.

Traynham said Mount Baldy is one of the Lakeshore's most visited sites and attracts about 180,000 visitors each year.